diff --git a/shell.nix b/shell.nix
index 381e5ca16a..590beb687d 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,4 +1,4 @@
-{ pkgs ? import ./nix/nixpkgs.nix, ... } @ args:
+{ pkgs ? import ./nix/nixpkgs.nix, llvmPackages ?pkgs.llvmPackages_9 } @ args:
 
 let
   lean = import ./default.nix args;